Definitely grab him, even if he continues his weak play, he's still a big enough name to offer to sweeten up a 2for1.

I'd actually consider dropping Yi. Dropping Sessions would leave you with two point guards and would give you too many sf/pf guys that do the same things: Dirk, Yi, Artest, Odom, Melo and even Peja all grab 6-10 boards and get you some threes.

That being said, if you feel that Yi is much more valueable for the future, you could always deal one or two of your similar sf/pf types for a PG when needed.

Pick him up, wait for him to have a big game and deal him for predraft value (maybe someone like Salmons?). That's what I would do with him. The guy definitely still has value, but I can see why someone would drop him if the league is shallow enough